JP2016143891A - Power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized power amplifier capable of improving characteristics of reception band noise.SOLUTION: A LB (Low Band)-side transmission signal system is configured such that an RC series circuit 16 constituted of a resistor 17 and a capacitor 18 is connected between a base terminal of a LBT (Low Band Transistor) 6 and a ground 19. This can improve characteristics of reception band noise without need for attachment of a resonance circuit constituted of an inductor and a capacitor with a large capacity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a multiband power amplifier having an amplification path for a plurality of RF signals (high frequency signals) and having a function of simultaneously using a plurality of transmission bands similar to carrier aggregation.

For example, in a transmission power amplifier mounted on a signal transmitter / receiver or the like that is a communication device, when transmitting an RF signal, the power of the RF signal leaks to a reception signal system (circuit on the signal reception side, etc.). Sometimes.
When the power of the RF signal leaking to the reception signal system increases, the reception band noise may deteriorate. Therefore, an allowable amount of power leakage to the reception signal system is defined.

  As one of the factors that degrade reception band noise, a signal having a frequency difference (hereinafter referred to as “difference frequency”) between the frequency of the transmission signal that is an RF signal and the frequency of the reception signal in the reception signal system is transmitted. It is mentioned that noise power at the frequency of the received signal is amplified by mixing with the transmission signal by a transistor that amplifies the signal.

In Patent Document 1 below, a method of attenuating a difference frequency component is proposed in order to reduce the power of reception band noise.
Specifically, Patent Document 1 discloses a power amplifier in which a series resonance circuit including an inductor and a capacitor whose resonance frequency is set to a difference frequency is connected to an input terminal of a transistor.
When such a series resonant circuit is connected to the input terminal of the transistor, the difference frequency signal is attenuated before being input to the transistor, so that the difference frequency signal and the transmission signal are mixed by the transistor. Noise components can be reduced. As a result, the characteristics of reception band noise are improved.

In recent years, since the number of components has increased remarkably with the enhancement of functions of terminals typified by smartphones and tablets, there has been an increasing demand for miniaturization of power amplifiers that amplify RF signals.
Also, in mobile terminals, there is an increasing demand for multiband power amplifiers that can support a plurality of bands in order to be able to support a plurality of bands simultaneously.
In multiband power amplifiers, in order to effectively use the transmission band, the amount of data communication has been increased by using a technique that simultaneously uses a plurality of transmission bands called carrier aggregation. Compared with the power amplifier of the above, it is expected that the reception band noise is deteriorated when the RF signal is transmitted.

Japanese Patent Laying-Open No. 2005-143079 (FIG. 1)

Since the conventional power amplifier is configured as described above, the differential frequency signal can be attenuated before being input to the transistor by the series resonance circuit including the inductor and the capacitor. However, a series resonant circuit composed of an inductor and a capacitor needs to resonate at a low frequency (for example, if the frequency of the transmission signal is 2.1 GHz and the frequency of the reception signal is 1.9 GHz, the frequency is 200 MHz. Large inductance and large capacitance are required, in which case many surface mount components (SMD) are required. Therefore, there is a problem that it is difficult to reduce the size of the power amplifier.
In addition, in order to support a plurality of bands, it is necessary to load a series resonance circuit having a resonance frequency that is the difference frequency of each band, so it is difficult to further reduce the size by increasing the number of parts. There was a problem of becoming.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a small power amplifier capable of improving the characteristics of reception band noise.

  A power amplifier according to the present invention includes: a first transistor that amplifies a first transmission signal; a second transistor that amplifies a second transmission signal having a frequency different from that of the first transmission signal; and A resonance circuit that is connected between the input terminal and the ground and resonates at a frequency that is a difference between the frequency of the first transmission signal and the frequency of the reception signal in the reception signal system, and between the input terminal of the second transistor and the ground A series circuit including a resistor and a capacitor is connected.

  According to the present invention, since the series circuit composed of the resistor and the capacitor is connected between the input terminal of the second transistor and the ground, a small power amplifier capable of improving the characteristics of the reception band noise is provided. There is an effect to be obtained.

It is a block diagram which shows the power amplifier by Embodiment 1 of this invention. It is a block diagram which shows the power amplifier by Embodiment 1 of this invention. It is a block diagram which shows the power amplifier by Embodiment 2 of this invention. It is a block diagram which shows the power amplifier by Embodiment 3 of this invention.

Hereinafter, in order to describe the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
1 is a block diagram showing a power amplifier according to Embodiment 1 of the present invention.
In FIG. 1, an HB RF input terminal 1 is a terminal for inputting an RF signal (first transmission signal) of HB (High Band).
The LB RF input terminal 2 is a terminal for inputting an LB (Low band) RF signal (second transmission signal) having a frequency lower than that of the HB RF signal input from the HB RF input terminal 1.
The HB input matching circuit 3 (indicated as “IMC_H” in the figure) is an input-side matching circuit connected to the HB RF input terminal 1.
The LB input matching circuit 4 (indicated as “IMC_L” in the drawing) is an input side matching circuit connected to the LB RF input terminal 2.

The first transistor HBT5 is a grounded heterojunction bipolar transistor having a base terminal (input terminal) connected to the HB input matching circuit 3 and a collector terminal connected to the HB output matching circuit 7. The HB RF signal input from the terminal is amplified, and the amplified RF signal is output from the collector terminal.
The second transistor HBT 6 is a grounded heterojunction bipolar transistor having a base terminal (input terminal) connected to the LB input matching circuit 4 and a collector terminal connected to the LB output matching circuit 8. The LB RF signal input from the terminal is amplified, and the amplified RF signal is output from the collector terminal.
In the first embodiment, an example in which the type of transistor that amplifies the RF signals of HB and LB is HBT will be described. However, the type of transistor is not limited to HBT, and for example, an FET or the like may be used. Good.

The HB output matching circuit 7 (indicated as “OMC_H” in the figure) is an output-side matching circuit connected to the HB RF output terminal 9.
The LB output matching circuit 8 (indicated as “OMC_L” in the figure) is an output side matching circuit connected to the LB RF output terminal 10.
The HB RF output terminal 9 is a terminal for outputting the HB RF signal amplified by the HBT 5.
The LB RF output terminal 10 is a terminal that outputs an LB RF signal amplified by the HBT 6.

The HB bias circuit 11 (denoted as “BC_H” in the figure) is a circuit that supplies a bias current to the HBT 5.
The LB bias circuit 12 (indicated as “BC_L” in the figure) is a circuit that supplies a bias current to the HBT 6.

The series resonant circuit 13 is connected between the base terminal of the HBT 5 and the ground 19, and the frequency of the HB RF signal input from the RF input terminal 1 for HB and the reception signal system (circuit on the signal receiving side, etc.) The circuit resonates at a frequency that is a difference from the frequency of the received signal in FIG.
The series resonance circuit 13 is configured by connecting an inductor 14 and a capacitor 15 in series.
The RC series circuit 16 is configured by connecting a resistor 17 and a capacitor 18 in series, and is connected between a base terminal of the HBT 6 and a ground 19.

Next, the operation will be described.
The series resonant circuit 13 is connected between the base terminal of the HBT 5 and the ground 19, and, like the series resonant circuit disclosed in Patent Document 1, the HB RF signal input from the HB RF input terminal 1. The resonance frequency is set so as to resonate at a difference frequency ΔFr _H (= Tx _H −Rx) that is a difference frequency between the frequency Tx _H of the received signal and the frequency Rx of the reception signal in the reception signal system.
By the resonance frequency of the series resonant circuit 13 is set to the difference frequency .DELTA.fr _H, in difference frequency .DELTA.fr _H, a reception band noise reduction circuit for HB impedance of the series resonant circuit 13 is reduced.

As a result, most of the signal of the difference frequency ΔFr _H does not flow to the HBT 5 but flows to the ground 19 through the series resonance circuit 13, so that the signal of the difference frequency ΔFr _H and the RF signal of the HB are mixed by the HBT 5. Almost disappears. Therefore, it is possible to reduce noise components generated by mixing in the HBT 5.
Note that the value of the capacitor 15 is set to 40 pF or more in order to prevent the impedance of the series resonance circuit 13 from being lowered and the electrical characteristics in the transmission band of the HB RF signal from being deteriorated at the difference frequency ΔFr _H. The value of the inductor 14 is selected so as to have a high impedance in the transmission band of the HB RF signal.

The RC series circuit 16 is an LB reception band noise reduction circuit configured by connecting a resistor 17 and a capacitor 18 in series.
The RC series circuit 16 secures the isolation from the HB transmission band while the frequency Tx _L of the LB RF signal input from the LB RF input terminal 2 and the frequency Rx of the reception signal in the reception signal system. At the difference frequency ΔFr _L (= Tx _L −Rx), which is the difference frequency, the value of the resistor 17 is adjusted between 40Ω and 100Ω in order to realize a low impedance.
Since the resistor 17 can be reduced in size by being realized by a resistor formed by the semiconductor process of the HBT 6, it can be made smaller than the inductor constituting the series resonance circuit.
The resistor 17 is provided to ensure isolation from the HB transmission band, and the capacitor 18 is provided to short-circuit the difference frequency ΔFr _L which is a low frequency.

By connecting the RC series circuit 16 having a low impedance at the difference frequency ΔFr _L between the base terminal of the HBT 6 and the ground 19, most of the signals of the difference frequency ΔFr _L do not flow to the HBT 6, and the RC series circuit 16 Therefore, the signal of the difference frequency ΔFr _L and the RF signal of the LB are hardly mixed by the HBT 6. Therefore, it is possible to reduce noise components generated by mixing in the HBT 6.

  As apparent from the above, according to the first embodiment, in the transmission signal system on the LB side, the RC series circuit 16 composed of the resistor 17 and the capacitor 18 is connected between the base terminal of the HBT 6 and the ground 19. Since it is configured, the characteristics of the reception band noise can be improved, and the power amplifier can be reduced in size.

  In the first embodiment, the HBT 5 is the first transistor, the HBT 6 is the second transistor, the series resonant circuit 13 is connected to the base terminal of the HBT 5, and the RC series circuit 16 is connected to the base terminal of the HBT 6. As shown in FIG. 2, the series resonant circuit 13 may be connected to the base terminal of the HBT 6 and the RC series circuit 16 may be connected to the base terminal of the HBT 5, with the HBT 5 as the second transistor and the HBT 6 as the first transistor. In this case, the same effect can be obtained.

In the first embodiment, the power amplifier corresponding to the transmission signal system on the HB side and the transmission signal system on the LB side is shown. However, the power amplifier corresponds to three or more transmission signal systems. May be.
In this case, if the reception band noise reduction circuit connected to at least one transmission signal system is the RC series circuit 16 configured by connecting the resistor 17 and the capacitor 18 in series, the first embodiment described above. Similarly to the above, it is possible to reduce the size of the power amplifier.

Embodiment 2. FIG.
3 is a block diagram showing a power amplifier according to Embodiment 2 of the present invention. In FIG. 3, the same reference numerals as those in FIG.
The RC series circuit 21 as the first series circuit is configured by connecting a resistor 22 and a capacitor 23 in series, and is connected between the base terminal of the HBT 5 and the ground 19.
The RC series circuit 24 as the second series circuit is configured by connecting a resistor 25 and a capacitor 26 in series, and is connected between the base terminal of the HBT 6 and the ground 19.

In the first embodiment, the reception band noise reduction circuit of one of the two transmission signal systems (the transmission signal system on the HB side or the transmission signal system on the LB side) includes the resistor 17 and the capacitor 18. In the second embodiment, the reception band noise reduction circuits of both transmission signal systems are configured as RC series circuits 21 and 24 including resistors and capacitors. Yes.
In this case, since the two transmission signal systems can be reduced in size, there is an effect that the size can be further reduced as compared with the first embodiment.

Embodiment 3 FIG.
4 is a block diagram showing a power amplifier according to Embodiment 3 of the present invention. In FIG. 4, the same reference numerals as those in FIG.
The bias applying transistor 31 constituting the LB bias circuit 12 is an emitter follower LB amplifying transistor, and supplies a bias current to the HBT 6.
In the emitter follower type bias circuit, a system in which a resistor 32 is loaded between the emitter terminal of the bias applying transistor 31 and the ground is often used as a temperature compensation circuit. In the third embodiment, one of the resistors 32 is used. The unit also serves as the resistor 17 of the RC series circuit 16.
Since part of the resistor 32 in the LB bias circuit 12 also serves as the resistor 17 of the RC series circuit 16, the size can be further reduced as compared with the first embodiment.

Here, an example is shown in which a part of the resistor 32 in the LB bias circuit 12 also serves as the resistor 17 of the RC series circuit 16, but the HB bias circuit 11 of FIG. 2 is the LB bias circuit shown in FIG. 12 may be configured such that a part of the resistor in the HB bias circuit 11 of FIG. 2 also serves as the resistor 17 of the RC series circuit 16 of FIG.
Also in this case, there is an effect that the size can be further reduced as compared with the first embodiment.

Similarly, the HB bias circuit 11 and the LB bias circuit 12 shown in FIG. 3 are configured in the same manner as the LB bias circuit 12 shown in FIG. 4, and some of the resistors in the HB bias circuit 11 shown in FIG. 3 may also serve as the resistor 22 of the RC series circuit 21 of FIG. 3, and a part of the resistor in the LB bias circuit 12 of FIG. 3 may also serve as the resistor 25 of the RC series circuit 24 of FIG.
In this case, there is an effect that the size can be further reduced as compared with the second embodiment.

  In the present invention, within the scope of the invention, any combination of the embodiments, or any modification of any component in each embodiment, or omission of any component in each embodiment is possible. .

  1 HB RF input terminal, 2 LB RF input terminal, 3 HB input matching circuit, 4 HB input matching circuit, 5 HBT (first transistor), 6 HBT (second transistor), 7 HB output Matching circuit, 8 LB output matching circuit, 9 HB RF output terminal, 10 LB RF output terminal, 11 HB bias circuit, 12 LB bias circuit, 13 series resonant circuit, 14 inductor, 15 capacitor, 16 RC series Circuit, 17 resistor, 18 capacitor, 19 ground, 21 RC series circuit (first series circuit), 22 resistor, 23 capacitor, 24 RC series circuit (second series circuit), 25 resistor, 26 capacitor, 31 Bias application Transistor, 32 resistors.

Claims (5)

A first transistor for amplifying a first transmission signal;
A second transistor for amplifying a second transmission signal having a frequency different from that of the first transmission signal;
A resonance circuit connected between the input terminal of the first transistor and the ground and resonating at a frequency that is a difference between the frequency of the first transmission signal and the frequency of the reception signal in the reception signal system;
A power amplifier comprising: a series circuit including a resistor and a capacitor connected between the input terminal of the second transistor and the ground.   The resistor connected between the emitter terminal of the bias applying transistor constituting the bias circuit for supplying a bias current to the second transistor and the ground also serves as the resistor of the series circuit. The power amplifier according to claim 1. A first transistor for amplifying a first transmission signal;
A second transistor for amplifying a second transmission signal having a frequency different from that of the first transmission signal;
A first series circuit comprising a resistor and a capacitor connected between the input terminal of the first transistor and the ground; and a second series comprising a resistor and a capacitor connected between the input terminal of the second transistor and the ground. A power amplifier comprising:   The resistor connected between the emitter terminal of the bias applying transistor constituting the bias circuit for supplying a bias current to the second transistor and the ground also serves as the resistor of the second series circuit. The power amplifier according to claim 3.   The resistor connected between the emitter terminal of the bias applying transistor constituting the bias circuit for supplying a bias current to the first transistor and the ground also serves as the resistor of the first series circuit. The power amplifier according to claim 3 or 4, wherein the power amplifier is provided.

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